Chasing and counting mesons

NEWPORT NEWS, VA – A doctoral dissertation on meson decay in the ongoing GlueX Collaboration at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility has just earned the prestigious 2023 Jefferson Science Associates (JSA) Thesis Prize.

Award-winner Karthik Suresh has been participating in GlueX since October 2018. His exemplary contributions to those experiments helped earn him a position as a postdoctoral research associate at William & Mary in September 2023.

Suresh is quick to share his success and achievement in GlueX with his Ph.D. mentors. Zisis Papandreou, a professor and head of the department of physics at the University of Regina, and Cristiano Fanelli, an assistant professor of data science and director of technology at William & Mary, both guided Suresh’s work on his research project and doctoral dissertation. 

In addition, Suresh credited two predecessors whose doctoral research laid the groundwork for his work: Ahmed M. Foda at the University of Regina in Canada and Amy M. Schertz at William & Mary. Kevin Scheuer, also at William & Mary, is continuing the same line of research and taking it forward.

“I should not take all of the credit, because this work has been a collaboration,” said Suresh.

The prize comes with an award of $2,500. Suresh delivered a talk about his dissertation, “Partial Wave Analysis of Neutral b1 Meson at GlueX,” at the 2024 annual meeting of the Jefferson Lab Users Organization (JLUO) in June.

The JLUO is a forum where more than 1,900 scientists from more than 324 institutions in 39 countries can exchange information regarding experimental, theoretical or applied research relevant to Jefferson Lab’s Continuous Electron Beam Accelerator Facility (CEBAF). JLUO’s larger goal is to promote the most effective use of CEBAF to advance the common good.

The JSA Thesis Prize was established in 1999 by the Southeastern Universities Research Association and is now one of many projects supported by the JSA Initiatives Fund Program, which was established by Jefferson Science Associates to support programs, initiatives and activities that further the scientific outreach, and promote the science, education and technology missions of Jefferson Lab in ways that complement its basic and applied research focus.

Chasing mesons

GlueX is being run in Jefferson Lab’s Experimental Hall D, and its main goal is to create a spectrum, or a sort of periodic table, of mesons — composite particles composed of a quark and an antiquark. 

Theoretical predictions of mesons don’t always agree, so GlueX is designed to help resolve discrepancies. Experimentalists shoot CEBAF’s powerful electron beam into the Hall D complex, where the electron beam is converted into a beam of photons. These photons are crashed into a target, and then nuclear physicists detect and analyze the cascade of mesons and other subatomic particles that result from the collision.

“The photon hits the proton, and there are these fragments that fly out of this collision,” Suresh explained. “The goal, in general, is to reconstruct the collision. But all we have access to is the accident site.”

Graduate students like Suresh are typically tasked with studying and mapping out specific channels of decay. These so-called channels are determined by a subatomic particle that has emerged from the collision and refers to how it changes or falls apart as it moves away from the collision site.

Suresh chose to study the channel for the neutral b1 meson as it decays into several other smaller particles. He used partial wave analysis for the challenging task of distinguishing between an actual b1 meson and others.

His award-winning thesis includes his work on GlueX, plus two other major components: his contributions to calibrating a barrel calorimeter that is used in GlueX and to using artificial intelligence to optimize the design of detectors used in the DOE’s Electron-Ion Collider (EIC) project.

The calorimeter is a 28-ton device used to measure a particle’s heat or energy. It was designed and built at the University of Regina, where Suresh earned his doctorate in hybrid meson spectroscopy.

The EIC is a next-generation particle accelerator that will study the strong nuclear force, or the “glue” that binds the building blocks of visible matter. It’s based at DOE’s Brookhaven National Laboratory and is being designed and built in partnership with Jefferson Lab.

This work on the EIC project earned Suresh his current postdoctoral position in William & Mary’s data science program.

How you count

The interface between theory and discovery is what fascinates Suresh.

“How we go from a theoretical prediction to how we can validate really excites me,” he said. “At the end of the day, how you count. We just count the number of particles that we see. And then, just by counting the number of particles you have made can provide or disprove a theoretical prediction.”

This pursuit echoes his first fascination with mathematics as a fourth grader under the tutelage of a “remarkable math teacher” in his hometown of Chennai, India.

“I understood I could go to a store; I could count money; I could exactly figure out the change I can expect in the store,” Suresh recalled. “That was really cool to me.”

In 10th grade, he opted to pursue courses in computer science and math. Afterward, he studied basic sciences at the University of Madras, where he earned a bachelor’s degree in physics in 2016, then a master’s degree at the Central University of Karnataka in 2018.

During his master’s program, he developed an algorithm in machine learning for the India-based Neutrino Observatory, or INO. This piqued his interest in particle physics and large-scale experiments and became a major reason why he joined GlueX while pursuing his doctorate at the University of Regina from 2018-2023.

He credits Justin Stevens, the Wilson & Martha Claiborne Stephens Associate Professor of Physics at William & Mary, for much of his doctoral success.

“Stevens was so, so, so helpful,” Suresh said. “He mentored me for two years straight, teaching me how to do analyses, getting to know this GlueX Collaboration. I feel that being in such a large-scale experiment with so many different collaborators, and especially having access to all of them, really is the way to learn. I don’t know if I was in a smaller collaboration or even a bigger collaboration like CERN that I would have had similar experiences, mainly because of the access to people here. I think that is super cool.”

-end-

Jefferson Science Associates, LLC, manages and operates the Thomas Jefferson National Accelerator Facility, or Jefferson Lab, for the U.S. Department of Energy’s Office of Science. JSA is a wholly owned subsidiary of the Southeastern Universities Research Association, Inc. (SURA).

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit https://energy.gov/science